The invention described herein may be manufactured and used by or for the Government of the United States of America for Governmental purposes without the payment of any royalties thereon or therefor.
(1) Field of the Invention
The present invention relates generally to manufactured parts, and more particularly to high-strength parts having exterior surfaces that are precision manufactured using a stereolithographic method/apparatus while having an interior core made from a high-strength material.
(2) Description of the Prior Art
Complex models can now be quickly and accurately made by linking computer-aided design (CAD) model specifications with a commercially available process known as stereolithography. A stereolithography apparatus (or SLA as it is known) takes CAD data and automatically produces a hard plastic pattern or model in a matter of hours. The patterns or models are three dimensional and include any design features that are made available by most general-use CAD systems. Examples of such SLA systems include those disclosed in U.S. Pat. No. 4,575,330 (Hull), U.S. Pat. No. 5,104,592 (Hull et al.), U.S. Pat. No. 5,216,616 (Masters), and U.S. Pat. No. 5,263,130 (Pomerantz et al.)
The basic concept of stereolithography is as follows. A part design is created on a CAD system and then downloaded to the control unit of an SLA. The control unit directs a movable laser beam onto the surface of a tank filled with a liquid polymer that is photo-curable. An elevator table resides just below the surface of the liquid polymer. In operation, the polymer solidifies to a thickness of approximately 0.005-0.030 inches wherever the laser beam strikes the surface of the liquid photo-curable polymer. To construct a cross-section of the part, the laser beam is scanned back and forth on the surface in the shape of the cross-section. The elevator table is then lowered a programmed amount so that the just-solidified cross-section is covered with the liquid polymer. Another cross-section of the part is then created on top of the first cross-section in the same manner as described above. The process continues until the complete part has been constructed. Finally, the part is removed from the tank and cured.
While producing complex parts accurately and quickly using stereolithography has many advantages, the cured polymer part does not typically provide the strength characteristics required of the actual part. Thus, functional testing of the SLA created part is not usually possible and must therefore be delayed until the part can be cast or machined from an appropriate strength material.
Accordingly, it is an object of the present invention to utilize the speed and accuracy of stereolithography in forming high-strength parts.
Another object of the present invention is to provide a method of making a precision manufactured part having the strength characteristics necessary for the functional testing of the part.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, high-strength parts are produced by first performing a stereolithography part generation process to create a polymer part having opposing interior surfaces. An uncured strength material is interposed between the opposing interior surfaces of the polymer part. The polymer part with the uncured strength material is then heated. The strength material is chosen to bond to the opposing interior surfaces during the heating step. The strength material comprises either a mixture of an epichlorohydrin resin, a catalyst and filler particles, or a mesh wetted with a catalyzed epichlorohydrin resin.